Fully integrated 50MHz frequency reference with 1ppm absolute accuracy within 0–80°C

In this paper, the design procedure and the simulation results of a fully integrated 50MHz frequency reference with 1ppm absolute accuracy within 0-80°C are reported. The frequency reference consists of a temperature compensated high frequency LC Colpitts oscillator. The temperature compensation scheme generates lookup-table based nonlinear control voltage for the inversion-mode MOS varactor of the LC oscillator. The system is designed within 0.35μm analog CMOS process. It consumes less than 8mA from 3.3V supply voltage. The reference frequency is derived by dividing the differential LC Colpitts oscillator output operating at 1.6GHz. The simulated phase noise of the 50MHz reference frequency is -115 dBc/Hz at 10 KHz offset.